If there's one thing I learned from being a mod, (not on this site) it's that if they don't listen to you the first time, report them. Don't spam up threads arguing with people. The people who use those images are regulars to the forum, and have already heard your side of the argument before. Besides, a talking-to by a moderator isn't a serious action. If they aren't habitually breaking the rules, it will only be a "this is against the rules, stop it" talk. But the only way to get most people to listen is to get real authority.